Telephone system.



V C. W. KECKLER. TELEPHONE SYSTEM.

APPLICATION FILED APR.26 1917.

Ill ,,@55 J @U, Patented Feb 5, 1918..

CHARLES W. KECKLER, OF NEWARK, NEW JERSEY, ASSIGNOT. TO WESTERN ELECTRIC COMPANY, INCORPORATED, 01E NEW YORK, N. Y., A CORPORATION 013 NEW YQRK.

TELEEHONE SYSTEM.

To (ZZZ whom it may concern: 7

Newark, in the county of Essex and State.

of New Jersey, have invented certain new and useful I1n1C rovements in Telephone Systems, of which the following is a full, clear, concise, and exact description.

This invention relates to telephone systems, and more particularly to such systems of the central energy type, its object being the pro vision of improved means for testing the busy or idle connectionof a called telephone line.

In accordance with the feature of this invention there is associated with a plurality of link circuits employed for connecting together telephone lines, a relay in a VVheatstone bridge. circuit common to the link circuits, which is responsive to the engagement of a link circuit with the terminal of a busy line to operatively associate a source of tone signaling current with an operators receiver.

This invention is illustrated in the accompanying drawing in which all apparatus is shown in its normal condition.

In the drawing there is shown a telephone line A, extending from a subscribers station to a central oliice, where it terminates in a plurality of jacks 16 and 26. At the central office there is a plurality of cord circuits B and C for connecting together telephone lines, it being understood, of course, that a plurality of lines, similar to line A, terminate at the central oflice. An operators telephone set shown in the lower dotted rectangle D is common to the cord circuits, and a WVheatstone bridge circuit shown in the upper dotted rectangle is also common to the cord circuits. Only three arms 5, 6 and 7 of the Wheatstone bridge circuit are normally connected therewith. A fourth arm is associated with the cord circuits.

Two relays 8 and 9 are permanently connected across the Wheatstone bridge circuit, relay 8 being normally energized by current over a path from battery through the bridge arm 5, windings of relays8 and 9, bridge arm 7 (the bridge arm 6 being connected in parallel with the windings 8 and 9 and the bridge arm 7), and the contact of the key 10 to ground. The contact of relay 8, is therefore, normally open. Relay 9 is marginal and does not attract its armature when in- Specification of Letters Patent.

Patented Feb... 5, 1918..

Application filed April 26, 1917. Serial 170. 16%,635.

cluded in the circuit just traced. Therefore, its contact is normally open. The contact of relay 8, when closed, establishes an operating circuit including a winding 11 of an induction coil 12, a second winding 13 of which is in circuit with receiver 14: of the operators telephone set. The closure of this contact sends an impulse of current from battery through winding 11 of the induction coil 12, whereupona tone produced in the operators receiver. The closure of the contact of the relay 8 may, therefore, be considered as opcratively associating a source of tone signaling current with the receiver 14 of the operators telephone set.

The fourth arm of the bridge may have two different values of resistance under differing conditions. If the plug 15 of cord circuit B be inserted into the jack 16 of line A, the fourth arm of the bridge will then be made up of the left-hand winding of relay 17 and the right-hand winding of the cut-off relay 18. The lefthand winding of relay 17 is of high resistance, while the right hand winding is of low resistance. Therefore relay 17 does not operate when its lefthand winding only is in circuit, but does opcrate when its right-hand winding is included in circuit. When the fourth arm of the bridge, consisting of the left-hand winding of relay 17 and the right-hand winding of cut-off relay 18. is connected to the bridge, the marginal relay 9 operates, thereupon completing an operating circuit through the right-hand winding of relay 17 which then operates and locks up through its right-hand alternate contact. In operating, relay 17 disconnects the lVheatstone bric ge circuit from cord circuit 13 and also disconnects the fourth arm from the bridge, restoring the bridge to normal. With the plug the cord circuit B connected witha jack of line A, cut-ofi' relay is operated to connect the sleeve terminals of the. jacks tot-he ring terminal thereof, so that the potential of these sleeve contacts is raised.

lit the operator, in testing the condition of line A, touches the tip contact of plug 15 of cord circuit C to the sleeve terminal of jack of line A, a fourth arm for the bridge will be estal ilished, which includes the winding of relay 27 the winding 28 of repeating coil E29 and the left-hand winding of relay 17 With this fourth arm connected to th hi'ids the resistance in the various arms is then such that there is no difference of potential at the terminals of relays 8 and 9. Relay 8 thereupon, releases its armature, completing tie hereinbeforc mentioned operating circuit, including the winding 11 of induction coil, whereupon a tone is produced in the operators receiver ll, indicating to the op-- erator that line A is busy.

The removal of the plug 15 of cord 01rcuit B from the jack 16 causes the deenergization of relay 17 and cut-oft relay l8,

' whereupon all apparatus is restoredtonormal position. Cut-off relay 18 is differentially' wound and does not attract its armature. when the receiver of the subscribers station is removed from the switchhook to initiate a call, but line relay 19 is then operated. The operator's telephone set may be connected with either cord circuit by the actuation of the p oper listening key 30.

What is claimed is: 1. A telephone system comprising a telephoneline terminating in a plurality of sets of terminals, a plurality of link circuits, one

being connected with one set of terminals,

7 an operators telephone set, a source of tone signaling current, a ll heatstone bridge circuit having three arms common to the link circuits, a fourth arm for the bridge connected therewith upon engagement of another link circuit with a terminal of another set, and means in the bridgeresponsive to the'conncction of the fourth arm therewith to operatlvely associate the source of tone signaling current withthe receiver-of the operators telephone set.

A telephone systen'rcomprising a telephone line terminating in a plurality. of

sets of terminals, a plurality of link circuits, one being connected with one set of terminals, an operators telephone set, a source of tone signaling current, a ll heatston'e bridge circuit having three arms common to the link circuits, a fourth arm for the bridge connected therewith upon engagement of another linkcircuit with a terminal of another set, anda relay in the bridge responsive to the connection of the fourth arm therewith to operatively associate the source of tone signaling current with the receiver of the operators telephone set.

o. A telephone system comprising a tele ,phone line-terminating in a plurality of rent with the receiver of the operators telephone set.

t. A telephone system comprising a telephone line terminating in a plurality of sets of terminals, a plurality of link circuits,

one being connected with one set of terminals, an operators telephone set, a source of tone signaling current, a Wheatstone bridge circuit commonto the link circuits, means for altering the electrical condition of the bridge upon the engagement of another link circuit with a terminal of another set, and a relay in the bridge responsive to the altered condition thereof to operativcly associate the source of tone signaling current with the receiver of the operators telephone set.

5. A telephone system comprising a telephone line terminating in a plurality of sets of terminals, a plurality of link circuits, one being connected with one set of terminals, an induction coil having two wimlings, a responsive device incircuit with one winding, a Wheatstone bridge circuit having three arms common to the link circuits, a fourth arm for the bridge connected therewith upon engagement of another link circuit with a terminal of another set, and means in the bridge responsive to the connection of the fourth arm therewith to complete an operating circuit including the other winding of the induction coil.

6. A telephone system comprising a Mile phone line terminating in a plurality of sets of terminals, a plurality of link circuits, one being connected with one set of terminals, an induction coil having two windings, a receiver in circuit with one winding. :1 \Vheatstone bridge circuit having three arms common to the link circuits, a fourth arm for the bridge connected therewith upon engagement of another link circuit with a terminal of another set, and a relay in the bridge responsive to the connection of the fourth arm therewith to complete an operating circuit including the other winding of the induction coil.

7. A telephone system comprising a telephone line terminating in a plurality of sets of terminals, a plurality of link circuits, one being connected with one set of termi nals, an induction coil having two windings, a responsive device in circuit with one winding, a lVheatstone bridge circuit common to the link circuits, means for altering the electrical condition of the bridge upon the engagement of another link circuit with a terminal of another set, and means in the bridge responsive to the altered condition thereof to complete an operating circuit including the other winding of the indiu-lion coil.

8. A telephone system comprising a telephone line terminating in a plurality of sets of terminals, a plurality of link circuits, one

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being connected. with one set of terminals, an induction coil having two windings, a receiver in circuit with one winding, a Wheatstone bridge circuit common to the link circuits, means for altering the electrical condition of the bridge upon the engagement of another link circuit with a terminal of another set, and a relay in the bridge responsive to the altered condition thereof to complete an operating circuit including the other winding of the induction coil.

A telephone system comprising a plurality of telephone lines, a plurality of link circuits for interconnecting the lines, a lVhcatstone bridge circuithaving three arms common to the link circuits, a fourth arm for the bridge connected therewith upon connection of one of the link circuits with one of the telephone lines, a switching device in the bridge responsive to the connection of the fourth arm therewith, and means in the engaged link circuit operating upon response of the switching device to disconnect the bridge from the engaged link circuit.

10. A telephone system comprising a plurality of telephone lines, a plurality of link circuits for interconnecting the lines, a VVheatstone bridge circuit having three arms common to the link circuits, a fourth arm for the bridge connected therewith upon connection of one of the link circuits with one of the telephone lines, a switching device in the bridge responsive to the connection of the fourth arm therewith, and a re lay in the engaged. link circuit operating upon response of the switching device to disconnect the fourth arm from the bridge.

11. A telephone system comprising a plurality of telephone lines, a plurality of link circuits for interconnecting the lines, a VVheatstone bridge circuit common to and normally connected with the link circuits, means for altering the electrical condition of the bridge upon connection of one of the link circuits with one of the lines, a switching device in the bridge responsive to the altered condition of the bridge, and means in the engaged link circuit operating upon response of the switching device to disconnect the bridge from the engaged link circuit.

12. A telephone system comprising a plurality of telephone lines, a plurality of link circuits for interconnecting the lines, a lVheatstonebridge circuit common to and normally connected with the link circuits, means for altering the electrical condition of the bridge upon connection of one of the link circuits with one of the lines, a switching device in the bridge responsive to the altered condition of the bridge, and a relay in the engaged link circuit operating upon response of the switching device to disconnect the bridge from the engaged link circuit.

13. A telephone system comprising a plurality of telephone lines, each terminating in a plurality of sets of terminals, a plurality of link circuits for interconnecting the lines, an operators telephone set, a lVheatstone bridge circuit common to and normally connected with the link circuits, a source of tone signaling current, means for altering the electrical condition of the bridge upon connection of one of the link circuits with one set of terminals of a telephone line, a switching device in the bridge responsive to the altered condition thereof, a relay in the engaged link circuit operating upon response of the switching device to disconnect the bridge from the engaged link circuit and to restore the bridge to normal condition, means for again altering the elec trical condition of the bridge upon the subsequent engagement of another link circuit with a terminal of another set associated with the engaged line, and means in the bridge responsive to the last mentioned altered condition thereof to operatively associate the source of tone signaling current and the receiver of the operators telephone set.

14. A telephone system comprising a plurality of telephone lines, each terminating in a plurality of sets of terminals, a plurality of link circuits for interconnecting the line, an operators telephone set, a Wheatstone bridge circuit normally connected to the link circuits and having three arms common thereto, a source of tone signaling current, a fourth arm for the bridge connected therewith upon connection of one'of the link circuits with one set of terminals of a telephone line, a relay in the bridge responsive to the connection of the fourth arm thereto, a relay in the engaged link circuit operating upon response of the bridge relay to disconnect the bridge from the engaged link circuit and the fourth arm from the bridge, another fourth arm for the bridge connected therewith upon the subsequent engagement of another link circuit with a terminal of another set associated with the engaged line, and another relay in the bridge responsive to the connection of the second mentioned fourth arm thereto to operatively associate the source of tone signaling current and the receiver of the operators telephone set.

In witness whereof, I hereunto subscribe my name this 25th day of April, A. D. 1917.

CHARLES lV. KECKLER.

topic-ii of this patent maybe obtained for five cents each, by addressing the Commissioner of Patents.

Washington, 3). G, 

